Hello,
I’m sharing with you my new integration: Clivet-BMS-Integration, which allows you to control a Clivet thermodynamic water heater via Modbus (RTU or TCP).
I installed a Clivet AQUA PLUS SWAN-2 190 water heater.
Since the control board is equipped with a 3-pin Modbus connector to connect an additional (and paid 
) module, the ELFOCONTROL3 EVO (a kind of remote display), I set about connecting my water heater to our Home Assistant platform.
Small Hack: The connector type on the control board isn’t a standard JST (it doesn’t clip in, I got caught out 
) but an XHB2.54-3Y (easily found at Chinese retailers).
This isn’t my first attempt at developing custom integrations via the Modbus protocol; I’ve already deployed and shared my integration on the Koolnova ducted heater.
This integration instantiates about 30 entities (controls, sensors, switches), representing, for the most part, the Modbus registers present in the installation manual. The integration’s README is quite comprehensive in describing each entity.
A little tip: This thermodynamic water heater looks exactly like the MIDEA COMBO RSJA2-16/190S (even in its installation manual and Modbus registers). I’m guessing this Clivet device is nothing more than a “rebranded” Midea! 
So the integration should also work for this Midea water heater.
This integration integrates seamlessly with HACS.
Please feel free to test it and give me feedback for those who have it.